We see through the cornea, which is the clear, central part of the front surface of the eye. Normally, the cornea has a dome shape, like a ball. Sometimes, however, the structure of the cornea is just not strong enough to hold this round shape and the cornea bulges outward like a cone. This condition is called keratoconus
What Causes Keratoconus?
Tiny fibers of protein in the eye called collagen help hold the cornea in place and keep it from bulging. When these fibers become weak, they cannot hold the shape and the cornea becomes progressively more cone shaped.
Keratoconus appears to run in families. If you have it and have children, it’s a good idea to have their eyes checked for it starting at age 10. The condition happens more often in people with certain medical problems, including certain allergic conditions. It's possible the condition could be related to chronic eye rubbing. Most often, though, there is no eye injury or disease that can explain why the eye starts to change.
Keratoconus usually starts in the teenage years. It can, though, begin in childhood or in people up to about age 30. It's possible it can occur in people 40 and older, but that is less common.
The changes in the shape of the cornea can happen quickly or may occur over several years. The changes can result in blurred vision, glare and halos at night, and the streaking of lights.
The changes can stop at any time, or they can continue for decades. In most people who have keratoconus, both eyes are eventually affected, although not always to the same extent. It usually develops in one eye first and then later in the other eye.